[unreadable] The goal of this Phase II program is the development of immunosensing microelectrode arrays for use in the screening of multiple tumor markers in blood, urine and tissue samples. The arrays are designed so that they perform electrochemical simultaneous multianalyte immunoassays (SMAI) for tumor markers from single, small volume samples. Electrochemical SMAI, which represents a major advance in immunoassay methodology, is important because it increases test throughput, reduces cost-per-test, and increases test efficiency. The arrays will increase the diagnostic value of tumor markers in cancer diagnosis, assessment of treatment, and basic research in molecular profiling, by allowing the simultaneous quantitative measurement of multiple groups of markers associated with the same types of cancer. The measurement of single tumor marker concentrations currently has limited diagnostic usefulness. The arrays address the primary limitation of existing protein arraying methods, which is concern about denaturing of proteins immobilized on 2-dimensional substrates, by using a hydrophilic 3-dimensional electrode matrix to immobilize proteins. The arrays also have other significant advantages, being highly sensitive, eliminating the need for expensive optical imaging equipment by using economical electrochemical detection methods, being unaffected by sample turbidity, quenching, or interference from absorbing and fluorescing compounds typically found in biological samples, and using instrumentation that is simple and easily miniaturized to circuit board level, facilitating the development economical microanalyzers and methodology for ultra-small sample amounts. [unreadable] The Phase I program demonstrated the feasibility of electrochemical SMAI to detect two different tumor markers in a single sample. The aim of the Phase II program is to refine this technology through the optimization of electrochemical immunosensor preparation and assay design, expansion of the Phase I array to a greater number of immunosensing electrodes, and the development of a prototype array for the simultaneous detection and quantification of multiple tumor markers. The Phase II will focus on developing a robust, reliable and reproducible assaying system. [unreadable] [unreadable] [unreadable]